161631558 has 96 divisors (see below), whose sum is σ = 408895200. Its totient is φ = 47234880.

The previous prime is 161631541. The next prime is 161631593. The reversal of 161631558 is 855136161.

161631558 is a `hidden beast` number, since 1 + 616 + 31 + 5 + 5 + 8 = 666.

It is a super-2 number, since 2×161631558² = 52249521083014728, which contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 189060 + ... + 189912.

It is an arithmetic number, because the mean of its divisors is an integer number (4259325).

Almost surely, 2^161631558 is an apocalyptic number.

161631558 is a gapful number since it is divisible by the number (18) formed by its first and last digit.

It is a practical number, because each smaller number is the sum of distinct divisors of 161631558, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (204447600).

161631558 is an abundant number, since it is smaller than the sum of its proper divisors (247263642).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

161631558 is a wasteful number, since it uses less digits than its factorization.

161631558 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 915 (or 898 counting only the distinct ones).

The product of its digits is 21600, while the sum is 36.

The square root of 161631558 is about 12713.4400537384. The cubic root of 161631558 is about 544.7225903522.

The spelling of 161631558 in words is "one hundred sixty-one million, six hundred thirty-one thousand, five hundred fifty-eight".